Soup Stock from Kitchen Scraps

Thursday evenings we have my mother-in-law over for dinner.  If the weather's too treacherous for her to drive, I make a casserole and we take dinner to her.  We've been doing this for five and a half years, since her husband died.  She's a sweet woman, but something of an introvert, and we just wanted to make sure that she got out more than her weekly trip to church. 
For tomorrow night's supper I'm making a Tuscan soup and it calls for 4 cups of chicken broth.  I was looking around the fridge and saw some bok choy (2 large bunches) and half a bag of baby spinach that are a bit past their prime, so I chopped those up, added three large carrots, a large onion, crushed garlic, four chicken bullion cups, black pepper, and enough water (about 6 cups) to cover the whole thing in a stock pot.   It's simmering as I type this and smells divine.  Fresh stock for soup is so much better than store bought, and not much work.  I particularly love the addition of bok choy because it adds a very mild cabbage-y flavor and plays perfectly off of the onion and carrot.  It's so rich and hearty.  This will be a perfect base for the Tuscan soup tomorrow.